1. Field of the Invention
The present invention relates to improved high temperature epoxy resin compositions, additives and methods useful in sealing subterranean zones penetrated by well bores.
2. Description of the Prior Art
Hardenable epoxy resin compositions are commonly used for sealing subterranean zones penetrated by well bores when the zones contain corrosive fluids. For example, waste liquids such as salt water and acidic materials are often disposed of by injecting them into disposal wells. Such disposal wells penetrate subterranean formations which accept large volumes of waste and are naturally separated from other subterranean formations. When a disposal well or other well containing corrosive fluids is completed in the conventional manner, i.e., a string of steel casing is cemented in the well bore utilizing a hydraulic cement slurry, both the cement and steel casing are subjected to severe corrosion. A result of such corrosion can be that the liquid waste materials leak into and contaminate formations containing useful fluids such as hydrocarbons or potable water.
In order to prevent the corrosion of metal casing and insulate it from corrosive fluids in a disposal well, it has heretofore been the practice to seal the casing in the well bore with a hardenable epoxy resin composition. Epoxy resin compositions are highly resistent to degradation by acids and other corrosive wastes and insure that the wastes being disposed of do not find their way into subterranean locations containing useful recoverable fluids.
The heretofore used epoxy resin compositions have been basically comprised of an epoxy resin, a liquid diluent for the epoxy resin which causes it to have a low enough viscosity to be pumpable and a hardening agent which causes the epoxy resin to harden after an initial period of time during which the composition can be pumped into a desired location. Such epoxy resin compositions and methods of using the compositions are described in U.S. Pat. No. 3,960,801 issued on Jun. 1, 1976 and U.S. Pat. No. 4,072,194 issued on Feb. 7, 1978, both to Cole, et al.
While the Cole, et al. epoxy resin compositions and methods have been used effectively for sealing subterranean zones penetrated by well bores over the years, the compositions have been limited to use in subterranean zones having circulating temperatures below about 190.degree. F. At circulating temperatures above about 190.degree. F., the heretofore utilized epoxy resin compositions have generally not remained pumpable for long enough times to be placed in desired subterranean locations. That is, the high temperatures encountered by the compositions have caused them to increase in viscosity and begin the hardening process too quickly to be placed into desired subterranean locations. The term "high temperatures" is used hereinafter to mean circulating temperatures above about 190.degree. F. Thus, there are needs for improved epoxy resin compositions and methods which can be utilized for sealing subterranean zones at high temperatures.